Selective removal of transition metal nitride materials

ABSTRACT

Exemplary etching methods may include flowing an oxygen-containing precursor into a processing region of a semiconductor processing chamber. The methods may include contacting a substrate housed in the processing region with the oxygen-containing precursor. The substrate may include an exposed region of a transition metal nitride and an exposed region of a metal. The contacting may form an oxidized portion of the transition metal nitride and an oxidized portion of the metal. The methods may include forming a plasma of a fluorine-containing precursor and a hydrogen-containing precursor to produce fluorine-containing plasma effluents. The methods may include removing the oxidized portion of the transition metal nitride to expose a non-oxidized portion of the transition metal nitride. The methods may include forming a plasma of a chlorine-containing precursor to produce chlorine-containing plasma effluents. The methods may include removing the non-oxidized portion of the transition metal nitride.

TECHNICAL FIELD

The present technology relates to semiconductor processes and equipment.More specifically, the present technology relates to selectively etchingtransition metal nitride materials.

BACKGROUND

Integrated circuits are made possible by processes which produceintricately patterned material layers on substrate surfaces. Producingpatterned material on a substrate requires controlled methods forremoval of exposed material. Chemical etching is used for a variety ofpurposes including transferring a pattern in photoresist into underlyinglayers, thinning layers, or thinning lateral dimensions of featuresalready present on the surface. Often it is desirable to have an etchprocess that etches one material faster than another facilitating, forexample, a pattern transfer process. Such an etch process is said to beselective to the first material. As a result of the diversity ofmaterials, circuits, and processes, etch processes have been developedwith a selectivity towards a variety of materials.

Etch processes may be termed wet or dry based on the materials used inthe process. For example, a wet etch may preferentially remove someoxide dielectrics over other dielectrics and materials. However, wetprocesses may have difficulty penetrating some constrained trenches andalso may sometimes deform the remaining material. Dry etches produced inlocal plasmas formed within the substrate processing region canpenetrate more constrained trenches and exhibit less deformation ofdelicate remaining structures. However, local plasmas may damage thesubstrate through the production of electric arcs as they discharge.

Thus, there is a need for improved systems and methods that can be usedto produce high quality devices and structures. These and other needsare addressed by the present technology.

SUMMARY

Exemplary etching methods may include flowing an oxygen-containingprecursor into a processing region of a semiconductor processingchamber. The methods may include contacting a substrate housed in theprocessing region with the oxygen-containing precursor. The substratemay include an exposed region of a transition metal nitride and anexposed region of a metal. The contacting may form an oxidized portionof the transition metal nitride and an oxidized portion of the metal.The methods may include forming a plasma of a fluorine-containingprecursor and a hydrogen-containing precursor to producefluorine-containing plasma effluents. The methods may include removingthe oxidized portion of the transition metal nitride to expose anon-oxidized portion of the transition metal nitride. The methods mayinclude forming a plasma of a chlorine-containing precursor to producechlorine-containing plasma effluents. The methods may include removingthe non-oxidized portion of the transition metal nitride.

The methods may include forming a plasma of the oxygen-containingprecursor. Plasma effluents may be flowed into the processing region toform the oxidized portion of the transition metal nitride and theoxidized portion of the metal. A temperature of processing may bereduced prior to forming the plasma of the fluorine-containing precursorand the hydrogen-containing precursor. A temperature within theprocessing region may be maintained at less than or about 300° C. duringeach removal operation. The transition metal nitride may includetitanium, tantalum, or hafnium. The metal may include tungsten ormolybdenum. Forming the plasma of the fluorine-containing precursor andthe hydrogen-containing precursor may be performed in a remote plasmaregion of the semiconductor processing chamber. Forming the plasma ofthe chlorine-containing precursor may be performed in the processingregion of the semiconductor processing chamber. The plasma of thefluorine-containing precursor and the hydrogen-containing precursor maybe formed at a first plasma power. The plasma of the chlorine-containingprecursor may be formed at a second plasma power less than the firstplasma power. Contacting the substrate with the oxygen-containingprecursor may be performed in a first semiconductor processing chamber.Each removal operation may be performed in a second semiconductorprocessing chamber.

Some embodiments of the present technology may encompass etchingmethods. The methods may include flowing an oxygen-containing gas into aprocessing region of a semiconductor processing chamber. The methods mayinclude contacting a substrate housed in the processing region with theoxygen-containing gas. The substrate may include an exposed region of atransition metal nitride and an exposed region of a metal. Thecontacting may form an oxidized portion of the transition metal nitrideand an oxidized portion of the metal. The methods may include forming aplasma of a first halogen-containing precursor and a hydrogen-containingprecursor in a remote plasma region of the semiconductor processingchamber to produce first halogen plasma effluents. The methods mayinclude removing the oxidized portion of the transition metal nitride toexpose a non-oxidized portion of the transition metal nitride. Themethods may include forming a plasma of a second halogen-containingprecursor in the processing region of the semiconductor processingchamber to produce second halogen plasma effluents. The methods mayinclude removing the non-oxidized portion of the transition metalnitride.

In some embodiments, the methods may include forming a plasma of theoxygen-containing gas in the processing region or in the remote plasmaregion of the semiconductor processing chamber. The transition metalnitride may include titanium, tantalum, or hafnium, and the metal mayinclude tungsten or molybdenum. The plasma of the firsthalogen-containing precursor and the hydrogen-containing precursor maybe formed at a first plasma power. The plasma of the secondhalogen-containing precursor may be formed at a second plasma power lessthan the first plasma power. The second plasma power may be less than orabout 100 W. A temperature within the processing region may bemaintained at less than or about 250° C. during each removal operation.

Some embodiments of the present technology may encompass etchingmethods. The methods may include oxidizing a portion of a transitionmetal nitride on a substrate positioned in a processing region of asemiconductor processing chamber to produce an oxidized portion of thetransition metal nitride. The methods may include forming a plasma of afluorine-containing precursor and a hydrogen-containing precursor in aremote plasma region of a semiconductor processing chamber to producefluorine-containing plasma effluents. The methods may include removingthe oxidized portion of the transition metal nitride. The methods mayinclude forming a plasma of a chlorine-containing precursor in theprocessing region of the semiconductor processing chamber to producechlorine-containing plasma effluents. The methods may include removing anon-oxidized portion of the transition metal nitride.

In some embodiments, a temperature within the processing region may bemaintained at less than or about 250° C. The methods may include forminga plasma of an oxygen-containing precursor within the semiconductorprocessing chamber to oxidize a portion of the transition metal nitride.The methods may include repeating the method for at least one additionalcycle.

Such technology may provide numerous benefits over conventional systemsand techniques. For example, the processes may allow a preciselycontrolled dry etch to be performed, which may remove discreet layers oftransition metal nitride materials. Additionally, the processes mayselectively remove transition metal nitride materials relative to othermetal and oxide materials on the substrate. These and other embodiments,along with many of their advantages and features, are described in moredetail in conjunction with the below description and attached figures.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the disclosedtechnology may be realized by reference to the remaining portions of thespecification and the drawings.

FIG. 1 shows a top plan view of one embodiment of an exemplaryprocessing system according to some embodiments of the presenttechnology.

FIG. 2A shows a schematic cross-sectional view of an exemplaryprocessing chamber according to some embodiments of the presenttechnology.

FIG. 2B shows a detailed view of a portion of the processing chamberillustrated in FIG. 2A according to some embodiments of the presenttechnology.

FIG. 3 shows a bottom plan view of an exemplary showerhead according tosome embodiments of the present technology.

FIG. 4 shows exemplary operations in a method according to someembodiments of the present technology.

FIGS. 5A-5D show schematic cross-sectional views of materials etchedaccording to some embodiments of the present technology.

Several of the figures are included as schematics. It is to beunderstood that the figures are for illustrative purposes, and are notto be considered of scale unless specifically stated to be of scale.Additionally, as schematics, the figures are provided to aidcomprehension and may not include all aspects or information compared torealistic representations, and may include additional or exaggeratedmaterial for illustrative purposes.

In the appended figures, similar components and/or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a letter thatdistinguishes among the similar components. If only the first referencelabel is used in the specification, the description is applicable to anyone of the similar components having the same first reference labelirrespective of the letter.

DETAILED DESCRIPTION

Selectively etching transition metal nitride is beneficial in a varietyof device process flows including in the formation of dynamic randomaccess memory, FinFETs, and many other devices. The transition metalnitride may be employed as a barrier layer to inhibit diffusion whilemaintaining significant conductivity when combined with a conductor inthe form of a line or via. Conventional processes utilizing halogenprecursors or plasma products to etch transition metal nitrides havetypically been limited by the low etch rate of transition metal nitridewith these materials, which may be limited to Angstrom-level etchingover relatively longer periods of time. This may cause increasedresidence time of halogen materials, including plasma effluents, whichmay increase contact with exposed materials on the substrate that aresought to be maintained. Additionally, as semiconductor structuresbecome more complex with an increasing number of exposed materials,selective removal of these materials may be challenged. For example,nitrides of transition metals such as titanium, tantalum, hafnium, andother materials may exhibit metal-like properties, which may reduce theefficacy of selective removal relative to other exposed metals, such astungsten, molybdenum, and other materials. Conventional technologiesoften excessively etch these other materials, or require multipleadditional patterning operations to protect these other exposedmaterials from etching.

The present technology overcomes these limitations by performing aselective etch process that initially oxidizes portions of the nitrideprior to performing an etch process, which may more quickly remove theoxidized material. The oxidation process may additionally oxidize othermetal materials that are exposed. Because metal oxides, such as tungstenoxide or molybdenum oxide, may be maintained relative to certain othertransition metal oxides, subsequent removal operations may be performedto remove the transition metal oxide and underlying transition metalnitride, while maintaining the metal oxide material. The etch maypreferentially remove the oxidized material, which may facilitate aprecisely controlled etch process that may be substantially limited percycle to an amount of the transition metal nitride that has beenoxidized. The etch process may be selective relative to dielectricmaterials as well as metals and other materials on the substrate.Additionally, the present technology may facilitate the removal at lowertemperatures than conventional techniques, which may allow the processto be performed with exposure of low-k or other limited thermal budgetmaterials.

Although the remaining disclosure will routinely identify specificmaterials and semiconductor structures utilizing the disclosedtechnology, it will be readily understood that the systems, methods, andmaterials are equally applicable to a number of other structures thatmay benefit from aspects of the present technology. Accordingly, thetechnology should not be considered to be so limited as for use with anyspecific processes or materials alone. Moreover, although an exemplarychamber is described to provide foundation for the present technology,it is to be understood that the present technology can be applied tovirtually any semiconductor processing chamber that may allow theoperations described.

FIG. 1 shows a top plan view of one embodiment of a processing system100 of deposition, etching, baking, and curing chambers according toembodiments. In the figure, a pair of front opening unified pods 102supply substrates of a variety of sizes that are received by roboticarms 104 and placed into a low pressure holding area 106 before beingplaced into one of the substrate processing chambers 108 a-f, positionedin tandem sections 109 a-c. A second robotic arm 110 may be used totransport the substrate wafers from the holding area 106 to thesubstrate processing chambers 108 a-f and back. Each substrateprocessing chamber 108 a-f, can be outfitted to perform a number ofsubstrate processing operations including the dry etch processesdescribed herein in addition to cyclical layer deposition, atomic layerdeposition, chemical vapor deposition, physical vapor deposition, etch,pre-clean, degas, orientation, and other substrate processes.

The substrate processing chambers 108 a-f may include one or more systemcomponents for depositing, annealing, curing and/or etching a dielectricfilm on the substrate wafer. In one configuration, two pairs of theprocessing chambers, e.g., 108 c-d and 108 e-f, may be used to depositdielectric material on the substrate, and the third pair of processingchambers, e.g., 108 a-b, may be used to etch the deposited dielectric.In another configuration, all three pairs of chambers, e.g., 108 a-f,may be configured to etch a dielectric film on the substrate. Any one ormore of the processes described may be carried out in one or morechamber separated from the fabrication system shown in differentembodiments. It will be appreciated that additional configurations ofdeposition, etching, annealing, and curing chambers for dielectric filmsare contemplated by system 100.

FIG. 2A shows a cross-sectional view of an exemplary process chambersystem 200 with partitioned plasma generation regions within theprocessing chamber. During film etching, e.g., titanium nitride,tantalum nitride, tungsten, silicon, polysilicon, silicon oxide, siliconnitride, silicon oxynitride, silicon oxycarbide, for example, a processgas may be flowed into the first plasma region 215 through a gas inletassembly 205. A remote plasma system 201 may optionally be included inthe system, and may process a first gas which then travels through gasinlet assembly 205. The inlet assembly 205 may include two or moredistinct gas supply channels where the second channel may bypass theremote plasma system 201, if included.

A cooling plate 203, faceplate 217, ion suppressor 223, showerhead 225,and a pedestal 265 or substrate support, having a substrate 255 disposedthereon, are shown and may each be included according to embodiments.The pedestal 265 may have a heat exchange channel through which a heatexchange fluid flows to control the temperature of the substrate, whichmay be operated to heat and/or cool the substrate or wafer duringprocessing operations. The wafer support platter of the pedestal 265,which may include aluminum, ceramic, or a combination thereof, may alsobe resistively heated in order to achieve relatively high temperatures,such as from up to or about 100° C. to above or about 1100° C., using anembedded resistive heater element.

The faceplate 217 may be pyramidal, conical, or of another similarstructure with a narrow top portion expanding to a wide bottom portion.The faceplate 217 may additionally be flat as shown and include aplurality of through-channels used to distribute process gases. Plasmagenerating gases and/or plasma excited species, depending on use of theremote plasma system 201, may pass through a plurality of holes, shownin FIG. 2B, in faceplate 217 for a more uniform delivery into the firstplasma region 215.

Exemplary configurations may include having the gas inlet assembly 205open into a gas supply region 258 partitioned from the first plasmaregion 215 by faceplate 217 so that the gases/species flow through theholes in the faceplate 217 into the first plasma region 215. Structuraland operational features may be selected to prevent significant backflowof plasma from the first plasma region 215 back into the supply region258, gas inlet assembly 205, and fluid supply system 210. The faceplate217, or a conductive top portion of the chamber, and showerhead 225 areshown with an insulating ring 220 located between the features, whichallows an AC potential to be applied to the faceplate 217 relative toshowerhead 225 and/or ion suppressor 223. The insulating ring 220 may bepositioned between the faceplate 217 and the showerhead 225 and/or ionsuppressor 223 enabling a capacitively-coupled plasma to be formed inthe first plasma region. A baffle may additionally be located in thefirst plasma region 215, or otherwise coupled with gas inlet assembly205, to affect the flow of fluid into the region through gas inletassembly 205.

The ion suppressor 223 may comprise a plate or other geometry thatdefines a plurality of apertures throughout the structure that areconfigured to suppress the migration of ionically-charged species out ofthe first plasma region 215 while allowing uncharged neutral or radicalspecies to pass through the ion suppressor 223 into an activated gasdelivery region between the suppressor and the showerhead. Inembodiments, the ion suppressor 223 may comprise a perforated plate witha variety of aperture configurations. These uncharged species mayinclude highly reactive species that are transported with less reactivecarrier gas through the apertures. As noted above, the migration ofionic species through the holes may be reduced, and in some instancescompletely suppressed. Controlling the amount of ionic species passingthrough the ion suppressor 223 may advantageously provide increasedcontrol over the gas mixture brought into contact with the underlyingwafer substrate, which in turn may increase control of the depositionand/or etch characteristics of the gas mixture. For example, adjustmentsin the ion concentration of the gas mixture can significantly alter itsetch selectivity, e.g., SiNx:SiOx etch ratios, Si:SiOx etch ratios, etc.In alternative embodiments in which deposition is performed, it can alsoshift the balance of conformal-to-flowable style depositions fordielectric materials.

The plurality of apertures in the ion suppressor 223 may be configuredto control the passage of the activated gas, i.e., the ionic, radical,and/or neutral species, through the ion suppressor 223. For example, theaspect ratio of the holes, or the hole diameter to length, and/or thegeometry of the holes may be controlled so that the flow ofionically-charged species in the activated gas passing through the ionsuppressor 223 is reduced. The holes in the ion suppressor 223 mayinclude a tapered portion that faces the plasma excitation region 215,and a cylindrical portion that faces the showerhead 225. The cylindricalportion may be shaped and dimensioned to control the flow of ionicspecies passing to the showerhead 225. An adjustable electrical bias mayalso be applied to the ion suppressor 223 as an additional means tocontrol the flow of ionic species through the suppressor.

The ion suppressor 223 may function to reduce or eliminate the amount ofionically charged species traveling from the plasma generation region tothe substrate. Uncharged neutral and radical species may still passthrough the openings in the ion suppressor to react with the substrate.It should be noted that the complete elimination of ionically chargedspecies in the reaction region surrounding the substrate may not beperformed in embodiments. In certain instances, ionic species areintended to reach the substrate in order to perform the etch and/ordeposition process. In these instances, the ion suppressor may help tocontrol the concentration of ionic species in the reaction region at alevel that assists the process.

Showerhead 225 in combination with ion suppressor 223 may allow a plasmapresent in first plasma region 215 to avoid directly exciting gases insubstrate processing region 233, while still allowing excited species totravel from chamber plasma region 215 into substrate processing region233. In this way, the chamber may be configured to prevent the plasmafrom contacting a substrate 255 being etched. This may advantageouslyprotect a variety of intricate structures and films patterned on thesubstrate, which may be damaged, dislocated, or otherwise warped ifdirectly contacted by a generated plasma. Additionally, when plasma isallowed to contact the substrate or approach the substrate level, therate at which oxide species etch may increase. Accordingly, if anexposed region of material is oxide, this material may be furtherprotected by maintaining the plasma remotely from the substrate.

The processing system may further include a power supply 240electrically coupled with the processing chamber to provide electricpower to the faceplate 217, ion suppressor 223, showerhead 225, and/orpedestal 265 to generate a plasma in the first plasma region 215 orprocessing region 233. The power supply may be configured to deliver anadjustable amount of power to the chamber depending on the processperformed. Such a configuration may allow for a tunable plasma to beused in the processes being performed. Unlike a remote plasma unit,which is often presented with on or off functionality, a tunable plasmamay be configured to deliver a specific amount of power to the plasmaregion 215. This in turn may allow development of particular plasmacharacteristics such that precursors may be dissociated in specific waysto enhance the etching profiles produced by these precursors.

A plasma may be ignited either in chamber plasma region 215 aboveshowerhead 225 or substrate processing region 233 below showerhead 225.Plasma may be present in chamber plasma region 215 to produce theradical precursors from an inflow of, for example, a fluorine-containingprecursor or other precursor. An AC voltage typically in the radiofrequency (“RF”) range may be applied between the conductive top portionof the processing chamber, such as faceplate 217, and showerhead 225and/or ion suppressor 223 to ignite a plasma in chamber plasma region215 during deposition. An RF power supply may generate a high RFfrequency of 13.56 MHz but may also generate other frequencies alone orin combination with the 13.56 MHz frequency.

FIG. 2B shows a detailed view 253 of the features affecting theprocessing gas distribution through faceplate 217. As shown in FIGS. 2Aand 2B, faceplate 217, cooling plate 203, and gas inlet assembly 205intersect to define a gas supply region 258 into which process gases maybe delivered from gas inlet 205. The gases may fill the gas supplyregion 258 and flow to first plasma region 215 through apertures 259 infaceplate 217. The apertures 259 may be configured to direct flow in asubstantially unidirectional manner such that process gases may flowinto processing region 233, but may be partially or fully prevented frombackflow into the gas supply region 258 after traversing the faceplate217.

The gas distribution assemblies such as showerhead 225 for use in theprocessing chamber section 200 may be referred to as dual channelshowerheads and are additionally detailed in the embodiments describedin FIG. 3 . The dual channel showerhead may provide for etchingprocesses that allow for separation of etchants outside of theprocessing region 233 to provide limited interaction with chambercomponents and each other prior to being delivered into the processingregion.

The showerhead 225 may comprise an upper plate 214 and a lower plate216. The plates may be coupled with one another to define a volume 218between the plates. The coupling of the plates may be so as to providefirst fluid channels 219 through the upper and lower plates, and secondfluid channels 221 through the lower plate 216. The formed channels maybe configured to provide fluid access from the volume 218 through thelower plate 216 via second fluid channels 221 alone, and the first fluidchannels 219 may be fluidly isolated from the volume 218 between theplates and the second fluid channels 221. The volume 218 may be fluidlyaccessible through a side of the showerhead 225.

FIG. 3 is a bottom view of a showerhead 325 for use with a processingchamber according to embodiments. Showerhead 325 may correspond with theshowerhead 225 shown in FIG. 2A. Through-holes 365, which show a view offirst fluid channels 219, may have a plurality of shapes andconfigurations in order to control and affect the flow of precursorsthrough the showerhead 225. Small holes 375, which show a view of secondfluid channels 221, may be distributed substantially evenly over thesurface of the showerhead, even amongst the through-holes 365, and mayhelp to provide more even mixing of the precursors as they exit theshowerhead than other configurations.

The chamber discussed previously may be used in performing exemplarymethods, including etching methods, although any number of chambers maybe configured to perform one or more aspects used in embodiments of thepresent technology. Turning to FIG. 4 is shown exemplary operations in amethod 400 according to embodiments of the present technology. Method400 may include one or more operations prior to the initiation of themethod, including front end processing, deposition, etching, polishing,cleaning, or any other operations that may be performed prior to thedescribed operations. The method may include a number of optionaloperations, which may or may not be specifically associated with someembodiments of methods according to the present technology. For example,many of the operations are described in order to provide a broader scopeof the processes performed, but are not critical to the technology, ormay be performed by alternative methodology as will be discussed furtherbelow. Method 400 may describe operations shown schematically in FIGS.5A-5D, the illustrations of which will be described in conjunction withthe operations of method 400. It is to be understood that the figuresillustrate only partial schematic views, and a substrate may contain anynumber of additional materials and features having a variety ofcharacteristics and aspects as illustrated in the figures.

Method 400 may or may not involve optional operations to develop thesemiconductor structure to a particular fabrication operation. It is tobe understood that method 400 may be performed on any number ofsemiconductor structures or substrates 505, as illustrated in FIG. 5A,including exemplary structures on which a transition metal nitrideremoval operation may be performed. Exemplary transition metal nitridesmay include one or more of titanium nitride, tantalum nitride, hafniumnitride, or other transition metal nitrides. Exemplary semiconductorstructures may include a trench, via, or other recessed features thatmay include one or more exposed materials. For example, an exemplarysubstrate may contain silicon or some other semiconductor substratematerial as well as interlayer dielectric materials through which arecess, trench, via, or isolation structure may be formed. Exposedmaterials at any time during the etch process may be or include metalmaterials, one or more dielectric materials, a contact material, atransistor material, or any other material that may be used insemiconductor processes.

For example, although shown as generic layers, FIG. 5A may illustrate alayer of transition metal nitride 510 overlying substrate 505 or someother semiconductor material. Additionally, an exposed metal 512 mayalso be included. Although the remaining disclosure will referencetitanium nitride, it is to be understood that the transition metalnitride 510 may also be tantalum nitride, hafnium nitride, or othertransition metal nitrides, in embodiments of the present technology, andthe process may involve removal of any of these transition metalnitrides with or alternatively to titanium nitride. Similarly, metal 512may be tungsten, molybdenum, or some other metal, and in someembodiments the material may be a metal oxide, or some otheroxide-containing material on the substrate. Accordingly, the remainingdisclosure is not to be considered limited to the specific examplesdescribed.

Substrate 505 may illustrate a dielectric material overlying one or moreother structures on a substrate, and it is to be understood that anynumber of materials may be formed beneath the structure illustrated. Insome embodiments, dielectric materials may be or include silicon oxide,or any other oxide or nitride through which patterning may occur. It isto be understood that the noted structure is not intended to belimiting, and any of a variety of other semiconductor structuresincluding transition-metal-containing materials or othermetal-containing materials are similarly encompassed. Other exemplarystructures may include two-dimensional and three-dimensional structurescommon in semiconductor manufacturing, and within which a transitionmetal-containing material, such as titanium nitride, is to be removedrelative to one or more other materials, as the present technology mayselectively remove transition metal nitrides relative to other exposedmaterials, such as silicon-containing materials, and any of the othermaterials discussed elsewhere. Additionally, although ahigh-aspect-ratio structure may benefit from the present technology, thetechnology may be equally applicable to lower aspect ratios and anyother structures.

For example, layers of material according to the present technology maybe characterized by any aspect ratios or the height-to-width ratio ofthe structure, although in some embodiments the materials may becharacterized by larger aspect ratios, which may not allow sufficientetching utilizing conventional technology or methodology. For example,in some embodiments the aspect ratio of any layer of an exemplarystructure may be greater than or about 10:1, greater than or about 20:1,greater than or about 30:1, greater than or about 40:1, greater than orabout 50:1, or greater. Additionally, each layer may be characterized bya reduced width or thickness less than or about 100 nm, less than orabout 80 nm, less than or about 60 nm, less than or about 50 nm, lessthan or about 40 nm, less than or about 30 nm, less than or about 20 nm,less than or about 10 nm, less than or about 5 nm, less than or about 1nm, or less. This combination of high aspect ratios and minimalthicknesses may frustrate many conventional etching operations, orrequire substantially longer etch times to remove a layer, along avertical or horizontal distance through a confined width. Moreover,damage to or removal of other exposed layers may occur with conventionaltechnologies as previously explained.

In some embodiments, the methods may include a multiple-operation etchprocess, which may control etching of the transition metal nitriderelative to other exposed materials, such as metal 512 or dielectricmaterials, for example silicon oxide, as well as other materials thatmay be exposed on the substrate during processing. Method 400 mayinclude flowing an oxygen-containing precursor into a semiconductorprocessing chamber housing the described substrate. In some embodimentsthe oxygen-containing precursor may be flowed directly to contact thesubstrate, although in some embodiments a plasma may be formed of theoxygen-containing precursor at optional operation 405. Theoxygen-containing precursor may be flowed through a remote plasma regionof the processing chamber, such as a remote plasma system unit or region215 described above, and a plasma may be formed of the oxygen-containingprecursor to produce plasma effluents. Although a substrate-level plasmamay be produced, in some embodiments the plasma may be a remote plasma,which may protect exposed substrate materials from ion bombardment thatmay occur due to the substrate-level plasma.

Whether plasma-enhanced or not, at operation 410 the oxygen-containingprecursor or plasma effluents of the oxygen-containing precursor may bedelivered to the substrate processing region, where the effluents maycontact the semiconductor substrate including an exposed transitionmetal material, such as an exposed region of titanium nitride. Thecontacting may produce an oxidized material, such as an oxidized surfaceon the titanium nitride or a titanium nitride oxide material, such as byconverting the exposed titanium nitride on the substrate. In someembodiments, subsequent the oxidation, the plasma may be extinguished,and the chamber may be purged. As shown in FIG. 5A, oxygen material, oroxygen plasma effluents 515 may be flowed to contact the exposedtitanium nitride material, which may convert an exposed surface oftransition metal nitride 510 into an oxidized titanium material 520, asshown in FIG. 5B, and which may include aspects of oxygen, transitionmetal, and nitrogen. Some portion of the nitrogen may also be outgassedas nitrous oxide, nitric oxide, or nitrogen dioxide. The oxidation mayalso form an oxidized portion 522 of the metal 512.

Subsequent the oxidation operation, the delivery of the oxygen materialmay be halted. Although the following operations may be performed in thesame chamber, in some embodiments in which a temperature change may beenacted, as will be described further below, the substrate may be movedto a second processing chamber, such as on the same mainframe orplatform, which may maintain the substrate under vacuum. Subsequent tohalting the oxygen plasma, or transfer of the substrate to anotherchamber, a first halogen-containing precursor may be flowed into theprocessing region. Similarly to the oxygen-containing precursor, thehalogen-containing precursor may be delivered directly to the processingregion, although in some embodiments the first halogen-containingprecursor may first be formed into a plasma at operation 415. The plasmamay also be generated in a remote plasma region of the processingchamber in some embodiments of the present technology. The etchantprecursor may interact with the oxidized portion of the titanium nitrideto produce byproducts including ammonium, titanium, oxygen and/or ahalogen, such as including titanium fluoride or titanium oxy-fluoride,and which may be volatile under certain processing conditions, and maybe evolved from the substrate. Accordingly, whether plasma enhanced ornot, the halogen-containing precursor may contact the oxidized material,which may etch or remove the oxidized region of the transition metalnitride material from the underlying metal at operation 420.

By utilizing a remote plasma to energize the first halogen-containingprecursor, in some embodiments the plasma effluents may be passedthrough an ion suppression element, such as ion suppressor 223 aspreviously described. This may filter out ionic species and deliverneutral and radical species to the processing region. Consequently, theremoval process performed may be substantially chemical in nature, andionic impact on the substrate may be minimized or prevented.Additionally, because biasing may not be utilized in some embodiments, amore isotropic removal may be performed. Because the oxidized portion522 of metal 512 may be a denser material than the oxidized transitionmetal nitride, the removal process may be performed to remove theoxidized portion of the transition metal nitride while substantiallymaintaining the oxidized portion 522 of metal 512, which may be morechemically resistant. By filtering out ions, the oxidized metal may alsobe protected from physical removal due to ionic impact, which mayfurther increase selectivity. For example, tungsten may form a denseoxide structure that may resist a controlled chemical etch process ofthe oxidized portion of the transition metal nitride, and which may havelimited or no physical etch component. As illustrated in FIG. 5C, ahalogen-containing precursor or plasma effluents 525 may contact theoxidized portion of the transition metal nitride and produce volatilebyproducts 530, and which may remove the oxidized material from thetransition metal nitride material, while substantially maintaining theoxidized portion 522 of metal 512. By first oxidizing the exposed metaland metal nitride materials, a selective removal of the oxidizedtransition metal nitride may be performed by a mostly chemicalinteraction. Accordingly, subsequent to the removal or partial removalof the oxidized portion of the transition metal nitride, an underlyingregion of the transition metal nitride may be exposed, while theoxidized portion 522 of metal 512 may provide a protective layer overthe metal during subsequent removal of the transition metal nitride.

After the oxidized portion of the transition metal nitride has beenremoved or at least partially removed to expose non-oxidized transitionmetal nitride, a second removal process may be performed to etch thetransition metal nitride. For example, a second halogen-containingprecursor may be delivered to the semiconductor processing chamber, anda plasma may be formed of the second halogen-containing precursor atoperation 425. The plasma may produce plasma effluents of the secondhalogen-containing precursor, which may contact and remove non-oxidizedregions of the transition metal nitride at operation 430. While thefirst halogen-containing plasma effluents may be formed remotely toallow filtering of the ionic species, in some embodiments the secondhalogen-containing plasma effluents may be formed in the processingregion. For example, a more aggressive precursor may be utilized in thesecond removal operation using the second halogen-containing precursor.By producing the plasma under low-power conditions, an amount ofphysical interaction with the transition metal nitride may facilitateremoval. The physical component may be controlled to reduce or limitbombardment of the oxidized portion of the metal, which may limit anyremoval of the metal material. For example, a bias plasma may be used todirect ionic species at the substrate, which may facilitate physicalremoval of the nitride material along with a chemical removal process.As shown in FIG. 5D, plasma effluents 535 of the secondhalogen-containing precursor may be directed at the substrate, and mayetch the transition metal nitride 510 that has been exposed. Although anamount of interaction, both chemical and physical, may occur with theoxidized portion 522 of the metal 512, the removal may be minimizedbased on the removal conditions.

The halogen-containing precursor or plasma effluents may be halted, andthe process may then be repeated in any number of cycles to removeadditional layers of the transition metal nitride selectively relativeto additional exposed materials. By performing multiple cycles, theselectivity to the metal or oxide may be increased. For example, asexplained above, the second removal operation may cause an amount ofremoval of the oxidized portion of the metal subsequent to an initiationor saturation period. By halting the process after a short period oftime, and repeating the process, the subsequent oxidation operation maycure or refresh the surface of the oxidized portion of the metal, andmay increase the oxide density. This may facilitate reduced removal ofthe metal over time, while allowing substantial removal of thetransition metal nitride during the cycles.

The precursors during any of the multi-step operation may includeoxygen-containing precursors, which may include any oxygen-containingmaterials or oxygen-containing gas in some embodiments. For example,non-limiting oxygen-containing precursors may include diatomic oxygen(O₂), ozone (O₃), water (H₂O), an alcohol, hydrogen peroxide (H₂O₂),nitrous oxide (N₂O), or any other oxygen-containing material. Exemplaryhalogen-containing precursors may include one or more of fluorine orchlorine in some embodiments, as well as any other halogen. Someexemplary precursors that may be utilized as the halogen precursors mayinclude halides such as hydrogen fluoride (HF), nitrogen trifluoride(NF₃), or any organofluoride, diatomic fluorine (F₂), brominetrifluoride (BrF₃), chlorine trifluoride (ClF₃), sulfur hexafluoride(SF₆), xenon difluoride (XeF₂), boron trichloride (BCl₃), tungstenpentachloride (WCl₅), tungsten hexachloride (WCl₆), diatomic chlorine(Cl₂), or any other chlorine-containing or fluorine-containingprecursor. As explained above, in some embodiments the first removaloperation may include a first halogen-containing precursor, and thesecond removal operation may include a second halogen-containingprecursor, which may be different from the first. For example, the firsthalogen-containing precursor may be a fluorine-containing precursor, andthe second halogen-containing precursor may be a chlorine-containingprecursor.

The precursors may be flowed together in a variety of combinations, andthe precursors also may be flowed with any number of additionalprecursors or carrier gases. Additional precursors may include diatomichydrogen, or a hydrogen-containing precursor, nitrogen, argon, helium,or any number of additional materials, although in some embodiments theprecursors may be limited to control side reactions or other aspectsthat may impact selectivity. By including hydrogen in the first removaloperation, such as with the first halogen material, which may be afluorine-containing material, etch rates of materials from fluorine maybe reduced or suppressed, which may provide further control on theextent of removal. Additionally, as underlying materials may at leastpartially etch in contact with fluorine radicals, for example,increasing the dilution may further inhibit reaction with underlyingmaterials. To protect additionally exposed materials, as well as toprotect the transition metal nitride underlying the oxidized material,hydrogen may be delivered at a flow rate greater than the flow rate ofthe halogen-containing precursor. For example, in some embodiments inwhich the halogen-containing precursor may be nitrogen trifluoride orany other halogen-containing material, a flow rate ratio of hydrogen tothe halogen material may be greater than or about 1.5:1, and a flow rateratio of hydrogen to the halogen material may be greater than or about2.0:1, greater than or about 2.5:1, greater than or about 3.0:1, greaterthan or about 3.5:1, greater than or about 4.0:1, greater than or about4.5:1, greater than or about 5.0:1, greater than or about 10.0:1, orhigher. The hydrogen radicals may also help passivate other exposedmaterials while fluorine interacts with the oxidized material.

Processing conditions may impact and facilitate etching according to thepresent technology. For example, the temperature at which the operationsare performed may impact the extent to which the reaction may occur.During the oxidation of the exposed surfaces, elevated temperature mayfacilitate the reaction, and may allow a plasma-free reaction to beperformed, which may further protect other exposed materials frombombardment or interaction with oxygen radicals. Accordingly, in someembodiments of the present technology, the contact operation with theoxygen precursor or oxygen plasma effluents may be performed atsubstrate, pedestal, and/or chamber temperatures above or about 200° C.,and may be performed at temperatures above or about 250° C., above orabout 300° C., above or about 350° C., above or about 400° C., above orabout 450° C., or higher, depending on a thermal budget of materials onthe substrate. The temperature may also be maintained at any temperaturewithin these ranges, within smaller ranges encompassed by these ranges,or between any of these ranges.

In some embodiments the contact operation with the first and secondhalogen precursors or halogen plasma effluents may be performed at thesame or different temperature than the contact operation with theoxygen. The contact operation with the halogens may also be plasmaenhanced or plasma free in embodiments, such as depending on the halogenprecursor utilized. Regardless, the interaction may be controlled insome embodiments by lowering the temperature of the substrate, althoughthe temperature may be higher during the halogen contact operation aswell. Because of the thermal mass of the substrate support, in someembodiments the contact operation with the halogen precursor or plasmaeffluents may be performed in a separate processing chamber to allowdifferent temperatures to be used, while minimizing time to stabilizedifferent chamber conditions. The separate chamber may still be on thesame platform, which may allow the substrate to be maintained at vacuumconditions throughout the process.

In many processes to remove transition metal nitride withhalogen-containing materials without oxidation, the temperature may bemaintained greater than 300° C., or the reaction may cease to proceed.However, by performing a controlled oxidation according to embodimentsof the present technology, the contact operation and removal may beperformed at temperatures of less than or about 300° C., and may beperformed at temperatures of less than or about 290° C., less than orabout 280° C., less than or about 270° C., less than or about 260° C.,less than or about 250° C., less than or about 240° C., less than orabout 230° C., less than or about 220° C., less than or about 210° C.,less than or about 200° C., or less. Additionally, by utilizing a lowertemperature for the removal operations, the oxidized portion of themetal may be substantially or essentially maintained during the firstremoval process, which may be a fluorination reaction. As temperatureincreases, the fluorine-containing plasma effluents can begin removingthe oxidized metal material as well.

The pressure within the chamber may also affect the operations performedas well as affect at what temperature the byproducts may evolve from thetitanium nitride surface. To facilitate the oxidation, which may bebased on plasma-enhanced precursors, a processing pressure may be lowerthan in the second removal operation utilizing the halogen-containingprecursor. By maintaining a lower pressure in the first operation, suchas during use of the oxygen precursor or oxygen plasma effluents,increased interaction at the substrate surface may be facilitated. Thelower pressure in the first portion of the method may increase themean-free path between atoms, which may increase energy and interactionat the film surface. By utilizing a higher pressure in the secondportion of the method, such as during use of the halogen precursor orplasma effluents, etch rate may be increased, which may increaseselectivity by limiting residence time of the halogen materials withinthe processing region and in contact with other exposed materials.

Accordingly, in some embodiments the pressure may be maintained belowabout 5 Torr during the oxidation, such as during operations 405-410,and the pressure may be maintained below or about 4 Torr, below or about3 Torr, below or about 2 Torr, below or about 1 Torr, below or about 0.5Torr, or less. The pressure may then be increased during the secondportion of the method, such as during operations 415-430, where thepressure may be maintained at a pressure of greater than or about 1Torr, and may be maintained at greater than or about 2 Torr, greaterthan or about 3 Torr, greater than or about 4 Torr, greater than orabout 5 Torr, greater than or about 6 Torr, greater than or about 7Torr, greater than or about 8 Torr, greater than or about 9 Torr,greater than or about 10 Torr, or higher. The pressure may also bemaintained at any pressure within these ranges, within smaller rangesencompassed by these ranges, or between any of these ranges.

When plasma effluents are utilized during one or both of the removaloperations, plasma power may be maintained at less than about 500 W. Bymaintaining a lower plasma power, sputtering may be controlled, andinteractions may be limited to superficial chemical reactions, which maybetter limit the extent of oxidation and/or etching through the titaniumnitride. Consequently, in some embodiments the plasma power may bemaintained at less than or about 450 W, less than or about 400 W, lessthan or about 350 W, less than or about 300 W, less than or about 250 W,less than or about 200 W, less than or about 150 W, less than or about100 W, or less. Additionally, different plasma powers may be used forthe different plasma operations.

For example, as explained above, the first plasma removal operation forremoving oxidized material may be performed at a higher plasma power.This may increase dissociation of the fluorine-containing material,especially when diluted with hydrogen as explained above. For example,in some embodiments, while maintaining the plasma power at less than orabout 500 W, the plasma power in the remote region, such as acapacitively-coupled remote region as explained previously, may begreater than or about 100 W, and may be greater than or about 200 W,greater than or about 300 W, or more. However, for the plasma of thechlorine-containing precursor for the second removal operation, a lowerplasma power may be used.

Chlorine plasma effluents may more readily etch a variety of materials,including tungsten oxide, or other exposed materials on the substrate.To limit the production of chlorine radicals, a lower plasma power maybe used, which may be less than or about 200 W, less than or about 100W, less than or about 80 W, less than or about 60 W, less than or about50 W, less than or about 40 W, less than or about 30 W, less than orabout 20 W, or less. This may limit the chemical removal of the oxidizedportion of the metal. However, for a remote plasma, such low powerplasma may cause recombination and limited exposure, which may reduce orlimit the removal of the transition metal nitride. Accordingly, byforming a bias plasma in the processing region, exposure of thetransition metal nitride to plasma effluents may be improved.Additionally, a bias plasma may provide an amount of directionality toionic species, providing physical interaction at the surface, and whichmay increase removal. Because the exposed metal material may be denserby nature, and may include a denser oxide structure, the low-powerplasma physical interaction may have limited impact on the oxidizedportion of the metal, while increasing removal of the transition metalnitride. Accordingly, a remote plasma during the fluorination operation,and a lower power direct plasma during the chlorination may greatlyimprove selectivity during the etch process.

Adding further control to the etch process, the secondhalogen-containing precursor, such as chlorine, may be delivered forlimited time, and may be delivered throughout the etch process eithercontinually or in a series of pulses, which may be consistent or varyingover time. By limiting the delivery window, interaction with the densermetal oxide may be limited, while removal of the transition metalnitride may occur. By following with an additional cycle as previouslyexplained, the metal oxide may be refreshed with the subsequentoxidation operation, which may further limit removal during the process.The timing during each cycle for removal with the secondhalogen-containing precursor may be limited to less than or about 30seconds, and may be limited to less than or about 25 seconds, less thanor about 20 seconds, less than or about 15 seconds, less than or about10 seconds, less than or about 5 seconds, or less. While thefluorination reaction may proceed for 1, 2, 5, 10, or 20 times thelength of any of these noted periods due to the ability of the metaloxide to resist the fluorination etching, by limiting the chlorinationoperation time period, increased transition metal nitride may be removedwhile further maintaining the metal material.

By performing operations according to embodiments of the presenttechnology, transition metal nitride may be etched selectively relativeto other materials, including other oxides and metal materials. Forexample, the present technology may selectively etch transition metalnitride relative to exposed regions of metals, such as tungsten ormolybdenum as non-limiting examples, dielectrics includingsilicon-containing materials such as silicon oxide, or other materials.Embodiments of the present technology may etch transition metal nitridesrelative to other exposed material at a rate of at least about 10:1, andmay etch the transition metal nitrides at a selectivity greater than orabout 50:1, greater than or about 100:1, greater than or about 150:1,greater than or about 200:1, or more. By performing etch operationsaccording to embodiments of the present technology, controlled removalof transition metal nitrides may be performed, while maintaining anumber of materials that may also be exposed on the substrate duringprocessing.

In the preceding description, for the purposes of explanation, numerousdetails have been set forth in order to provide an understanding ofvarious embodiments of the present technology. It will be apparent toone skilled in the art, however, that certain embodiments may bepracticed without some of these details, or with additional details.

Having disclosed several embodiments, it will be recognized by those ofskill in the art that various modifications, alternative constructions,and equivalents may be used without departing from the spirit of theembodiments. Additionally, a number of well-known processes and elementshave not been described in order to avoid unnecessarily obscuring thepresent technology. Accordingly, the above description should not betaken as limiting the scope of the technology. Additionally, methods orprocesses may be described as sequential or in steps, but it is to beunderstood that the operations may be performed concurrently, or indifferent orders than listed.

Where a range of values is provided, it is understood that eachintervening value, to the smallest fraction of the unit of the lowerlimit, unless the context clearly dictates otherwise, between the upperand lower limits of that range is also specifically disclosed. Anynarrower range between any stated values or unstated intervening valuesin a stated range and any other stated or intervening value in thatstated range is encompassed. The upper and lower limits of those smallerranges may independently be included or excluded in the range, and eachrange where either, neither, or both limits are included in the smallerranges is also encompassed within the technology, subject to anyspecifically excluded limit in the stated range. Where the stated rangeincludes one or both of the limits, ranges excluding either or both ofthose included limits are also included.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural references unless the context clearly dictatesotherwise. Thus, for example, reference to “a precursor” includes aplurality of such precursors, and reference to “the layer” includesreference to one or more layers and equivalents thereof known to thoseskilled in the art, and so forth.

Also, the words “comprise(s)”, “comprising”, “contain(s)”, “containing”,“include(s)”, and “including”, when used in this specification and inthe following claims, are intended to specify the presence of statedfeatures, integers, components, or operations, but they do not precludethe presence or addition of one or more other features, integers,components, operations, acts, or groups.

1. An etching method comprising: flowing an oxygen-containing precursorinto a processing region of a semiconductor processing chamber;contacting a substrate housed in the processing region with theoxygen-containing precursor, wherein the substrate comprises an exposedregion of a transition metal nitride and an exposed region of a metal,and wherein the contacting forms an oxidized portion of the transitionmetal nitride and an oxidized portion of the metal; forming a plasma ofa fluorine-containing precursor and a hydrogen-containing precursor toproduce fluorine-containing plasma effluents; removing the oxidizedportion of the transition metal nitride to expose a non-oxidized portionof the transition metal nitride; forming a plasma of achlorine-containing precursor to produce chlorine-containing plasmaeffluents; and removing the non-oxidized portion of the transition metalnitride.
 2. The etching method of claim 1, further comprising: forming aplasma of the oxygen-containing precursor, wherein plasma effluents areflowed into the processing region to form the oxidized portion of thetransition metal nitride and the oxidized portion of the metal.
 3. Theetching method of claim 2, wherein a temperature of processing isreduced prior to forming the plasma of the fluorine-containing precursorand the hydrogen-containing precursor.
 4. The etching method of claim 3,wherein a temperature within the processing region is maintained at lessthan or about 300° C. during each removal operation.
 5. The etchingmethod of claim 1, wherein the transition metal nitride comprisestitanium, tantalum, or hafnium.
 6. The etching method of claim 1,wherein the metal comprises tungsten or molybdenum.
 7. The etchingmethod of claim 1, wherein forming the plasma of the fluorine-containingprecursor and the hydrogen-containing precursor is performed in a remoteplasma region of the semiconductor processing chamber.
 8. The etchingmethod of claim 1, wherein forming the plasma of the chlorine-containingprecursor is performed in the processing region of the semiconductorprocessing chamber.
 9. The etching method claim 1, wherein the plasma ofthe fluorine-containing precursor and the hydrogen-containing precursoris formed at a first plasma power, and wherein the plasma of thechlorine-containing precursor is formed at a second plasma power lessthan the first plasma power.
 10. The etching method claim 1, whereincontacting the substrate with the oxygen-containing precursor isperformed in a first semiconductor processing chamber, and wherein eachremoval operation is performed in a second semiconductor processingchamber.
 11. An etching method comprising: flowing an oxygen-containinggas into a processing region of a semiconductor processing chamber;contacting a substrate housed in the processing region with theoxygen-containing gas, wherein the substrate comprises an exposed regionof a transition metal nitride and an exposed region of a metal, andwherein the contacting forms an oxidized portion of the transition metalnitride and an oxidized portion of the metal; forming a plasma of afirst halogen-containing precursor and a hydrogen-containing precursorin a remote plasma region of the semiconductor processing chamber toproduce first halogen plasma effluents; removing the oxidized portion ofthe transition metal nitride to expose a non-oxidized portion of thetransition metal nitride; forming a plasma of a secondhalogen-containing precursor in the processing region of thesemiconductor processing chamber to produce second halogen plasmaeffluents; and removing the non-oxidized portion of the transition metalnitride.
 12. The etching method of claim 11, further comprising: forminga plasma of the oxygen-containing gas in the processing region or in theremote plasma region of the semiconductor processing chamber.
 13. Theetching method of claim 11, wherein the transition metal nitridecomprises titanium, tantalum, or hafnium, and wherein the metalcomprises tungsten or molybdenum.
 14. The etching method of claim 11,wherein the plasma of the first halogen-containing precursor and thehydrogen-containing precursor is formed at a first plasma power, andwherein the plasma of the second halogen-containing precursor is formedat a second plasma power less than the first plasma power.
 15. Theetching method of claim 14, wherein the second plasma power is less thanor about 100 W.
 16. The etching method of claim 11, wherein atemperature within the processing region is maintained at less than orabout 250° C. during each removal operation.
 17. An etching methodcomprising: oxidizing a portion of a transition metal nitride on asubstrate positioned in a processing region of a semiconductorprocessing chamber to produce an oxidized portion of the transitionmetal nitride; forming a plasma of a fluorine-containing precursor and ahydrogen-containing precursor in a remote plasma region of asemiconductor processing chamber to produce fluorine-containing plasmaeffluents; removing the oxidized portion of the transition metalnitride; forming a plasma of a chlorine-containing precursor in theprocessing region of the semiconductor processing chamber to producechlorine-containing plasma effluents; and removing a non-oxidizedportion of the transition metal nitride.
 18. The etching method of claim17, wherein a temperature within the processing region is maintained atless than or about 250° C.
 19. The etching method of claim 17, furthercomprising: forming a plasma of an oxygen-containing precursor withinthe semiconductor processing chamber to oxidize a portion of thetransition metal nitride.
 20. The etching method of claim 17, furthercomprising: repeating the method for at least one additional cycle.